The present invention relates to a field emission display and fabricating methods therefor, and more particularly, to a field emission display having improved field emission effect of a micro tip owing to a tunnelling effect of multiple gate electrodes and fabricating methods therefor.
Japanese Patent Laid-Open Publication No. hei 6-84454 discloses a field emission display of a typical Spindt type. As shown in FIG. 1, in the field emission display of the conventional Spindt type, a plurality of cathode layers 1 are provided on a substrate 9, and a plurality of resistive layers 2 are provided on each cathode layer 1. A micro tip 5 is formed on each resistive layer 2. The micro tip 5 is housed inside a well 3a in a gate insulating layer 3 provided on the deposited layers. A gate electrode 4 having a hole 4a corresponding to the cavity 3a is deposited on the gate insulating layer 3.
In such a conventional field emission display, field emission from the micro tip 5 due to an electric field induced by a voltage difference between the cathode layer 1 and the gate electrode 4 is obtained. Since an electric field between the gate electrode 4 and the micro tip 5 is formed by a single gate electrode 4, the field is concentrated on a tip portion 6 of the micro tip 5. Thus, emission of electrons due to the tunnelling effect at the tip 5 becomes difficult.
That is, an electric barrier is formed since the field is mainly applied to the tip portion 6 of the micro tip 5 and electrons are transferred from the lower portion of the micro tip 5 to the upper portion thereof. Thus, the electrons do not sufficiently concentrate on the tip portion 6 of the micro tip 5. To overcome the deterioration in mobility of electrons due to the electric barrier, an application voltage should be increased to form a strong electric field. Accordingly, consumption of electric power increases as well as mass generation of Joule heat thereby causing thermal degradation. Also, when a higher voltage is applied, the problem of leakage currents occurs. That is, electric current can be leaked through the gate insulating layer 3 between the cathode layer 1 and the gate electrode 4.
The current leakage through the gate insulating layer 3 can be overcame by thickening the gate insulating layer 3 beyond a particular value as shown in U.S. patent Ser. No. 5,064,396. However, when the thickness of the gate insulating layer 3 is increased, physical stress is generated therein thereby curtailing the life span of the display.